This invention relates to a socket having a contact for making contact to electrical part and more particularly to a socket for use in an IC chip test.
In recent years, the IC package has become thinner and smaller thereby increasing the demand for surface mounting of them. At the same time, however, the quality of the product becomes potentially less stable as the IC becomes thinner with the consequence that it has become even more important to testing and elimination of those products which do not pass test or which contain an element that does not pass test.
To accomplish such testing the IC package is placed in a heating furnace (heat-resistant test called burn-in test) in a socket. Such a socket for IC package mounting as used in such a test is shown in FIG. 15.
The IC package 16 as shown in FIG. 15 is of the vertical surface mount package type (VPAK), whereby a lead 18 is provided only on one side of the IC chip so as to be mounted vertically on the substrate as shown in FIG. 11, 12 and 13.
Protrusions 17a are provided at both ends of the main body 17 on the side with contact leads 18. Additionally, the leads 18 have a tip portion 18a bent by nearly 90 degrees with regard to the main portion of lead 18. FIG. 14 clearly shows this feature. The IC package 16 is mounted vertically in application on a printed substrate which is indicated by an imaginary line in FIG. 12. In this mounted state, the protrusion 17a are inserted into the blind holes 80a of the printed substrate 80, with the IC package 16 being positioned with regard to printed substrate 80 so that the bend part 18a at the tip of lead 18 is soldered to the wiring 80b of the printed substrate 80. In connection with the burn-in test, however, the IC package 16 is horizontally mounted as shown in FIG. 15.
FIG. 15 shows an expanded cross section of a typical socket with an IC package mounted therein. The socket consists of a main socket body (base) 81 which is equipped with a contact and a cover 90. The cover is biased in a direction which is opposite to the base 81 by means of a coil spring 98 and it is stopped at a prescribed location as compared with base 81 by means of a stopper as is known in the art and not shown in the drawing.
The IC package 16 is inserted into an IC package insertion space 81a of base 81 and positioned on a placing surface 81c of a placing stand 81b. Contact 95 has a base part 95a contained in the bottom wall of base 81, a terminal portion 95f which sticks out beneath the base and a pin part 95b which extends up into the space inside the base. Attached to pin part 95b is a curved portion 95c which terminates in a tip which compressively contacts the bent portion at the tip of lead 18 due to the elasticity of the pin part 95b.
In the above described socket, the lead 18 exists only on one side of the main IC package with a result that the main IC package body 17 tends to jump out upwardly by moving as indicated by arrow mark b by the compressive force due to the contact 95 as indicated by an arrow mark a.
It is possible to employ a latch mechanism and fix the position of the IC package by using it. However, the use of such a latch will complicate the structure of the socket and thereby increase its manufacturing cost.